It is well-known to operate inlet and exhaust valves of an internal combustion engine by means of a rotating camshaft. In many older designs of engine, the rotation of the cam shaft is mechanically coupled to that of the crankshaft and it is not possible to alter valve timing in relation to engine speed or loading. However, greater efficiency can be achieved by varying the valve operation with regard to the demands on the engine.
In order to give greater control over the valve actuation, it has been proposed to operate the valves using electromagnetic solenoid actuators governed by a computer-controlled engine management system. An alternative approach is described in WO 2004/097184. This relates to an electromagnetic actuator having a driven rotor which is coupled to the valve by a suitable linkage.